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Rotatory and Circular Motion


Here you will get to know about rotatory and circular motion, its types and the difference between both.

Rotatory Motion

A type of motion in which a body moves around a fix point in it's own axis is known as rotatory motion or when every part/point of the body is rotating around one fixed point is known as rotatory motion. Some of the examples of rotatory motion are as follow:

  • Earth moving in it's own axis around the sun.

  • A fan rotating around one fixed point.

  • The motion of car wheel and it's steering is another example of rotatory motion.

There are two types of rotatory motion which are as follow:

Spin: When a body is moving around it's own axis then it is called spin motion.

Orbital: When a body moves around a fix rotational path then that type of movement is orbital motion.

Circular Motion

A type of motion which is around a circular path is known as circular motion. it can either be uniform circular motion or non-uniform. it can also be described as curvilinear motion in which the radius remains constant. In this case there is an acceleration towards the center of ω2r. This gives rise to a force towards the center known as the centripetal force. This force is reacted to by what is called the centrifugal reaction. Some of the examples of circular motion are as follow:

  • A man made satellite moving around the earth in space.

  • A car moving in round-about.

  • Rotation of fan blades in a constant speed.

There are two types of circular motion that are explained below:

Uniform Circular Motion: In this type of circular motion the angular rate of rotation and speed is constant for the body.

Non-Uniform Circular Motion: When the speed of the body and rate of angular rotation keeps changing so this type of motion is known as non-uniform circular motion.


Problem: What is the angular velocity of a particle in a circular orbit, rotating at the rate of 200 times per minute?

Solution:

As the frequency of rotation is already given which is 200 times per minute so,

ω=2πf

ω=2π(200/60)

ω=20.93 Rad/s


Difference between Rotational and Circular Motion

According to Physics both types of motion are distinct although their are similarities between both motions but their are significant variances as well. The main difference between the circular and rotational motion is that in circular motion the body rotates around another body in a circular path while in rotational motion the body revolves/rotates around a specific point within the body.


Formulas related to these types of motions:

  1. τ = r F sin θ : r is the magnitude of the lever arm while F is the force on it and θ is the angle between both.

  2. ω=2πf

  3. a c = v 2 r



 

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